Short answers, pulled from the story.
Franco Fabbri proposed a definition of the musical genre that is now considered to be normative. He stated that a musical genre is a set of musical events whose course is governed by a definite set of socially accepted rules.
The proliferation of popular music in the 20th century has led to over 1,200 definable subgenres of music. A subgenre is a subordinate within a genre that adopts its basic characteristics but also has its own set of characteristics that clearly distinguish it.
Country music originated in the southern United States in the early 1920s. Its origin stems from European folk music combined with blues and spirituals of African Americans.
Soca music originated in Trinidad and Tobago in the 1970s. It was created by Ras Shorty I in an effort to revive traditional calypso.
Vincenzo Caporaletti proposed a theory named Audiotactile Music Theory which categorises music in three different branches: written music like classical music, oral music like folk music before sound recording technologies, and Audiotactile music where the process of production and transmission is pivoted around sound recording technologies.